Why air-conditioning/ventilation systems don’t always mean clean air

Ventilation or air-conditioning systems, if poorly designed or maintained, can be a source of contamination.  The resulting poor air quality may cause ill health symptoms such as headaches, eye nose throat or skin irritation, allergies coughs or wheezing.

Localised air currents can cause draughts, producing muscle tension and skin irritation. Contamination of ventilation systems with micro-organisms can give rise to outbreaks of humidifier fever or Legionellosis.

The Workplace (Health, Safety and Welfare) Regulations 1992 requires effective and suitable provision to be made to ensure that every enclosed workplace is ventilated by a sufficient quantity of fresh or purified air and that any plant used for the purpose shall include an effective device to give visible or audible warning of its failure where necessary for reasons of health or safety.

The ACOP to the regulations recommends that ventilation and air-conditioning systems are regularly cleaned, tested and maintained to ensure that they are free from anything which may contaminate the air.  Air taken into the building should be free from impurities that are likely to be offensive or cause ill health. Air inlets should not be sited near to traffic at ground level, flues or other sources of emission.  Intake air should also be filtered.  Poor or inadequate maintenance of the air handling system is a frequent cause of contamination. Microbial contamination can occur and particulate materials and other debris can build up in the ducting of ventilation systems. Filters must be cleaned and replaced as necessary while the risks from legionella and other bacterial contaminants must be controlled.

It is important that ventilation system ductwork can be examined internally to ensure that cleanliness is maintained and contaminants are not circulated around the building. Duct-work cleaning is, however, very expensive and should not be undertaken unless there is evidence that the ventilation system is excessively dirty and that this is posing a risk to health. Dirty marks around air supply vents, for instance, may indicate a problem.